KR20050039293A - Grease composition for actuator - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease composition for an actuator. More specifically, synthetic hydrocarbon oil is used instead of ester oil as base oil, and a lithium thickener and a PMA (Poly Metha-Acrylate) copolymer are added thereto. The present invention relates to a grease composition which improves the compatibility with various materials including plastics, and can extend the lubrication life at high and low temperatures and greatly improves adhesiveness, noiseless operation and durability.

Description

Grease composition for actuator

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a grease composition for an actuator. More specifically, synthetic hydrocarbon oil is used instead of ester oil as base oil, and a lithium thickener and a PMA (Poly Metha-Acrylate) copolymer are added thereto. The present invention relates to a grease composition which improves the compatibility with various materials including plastics, and can extend the lubrication life at high and low temperatures and greatly improves adhesiveness, noiseless operation and durability.

In recent years, miniaturization and weight reduction of automotive electronics has been pursued in accordance with the demand for light weight of automobiles, but in order to achieve high output efficiency in terms of performance, a method of supplementing the reduction of output due to miniaturization by rotating at high speed has been adopted. For this reason, automotive electronics that can withstand high-speed rotation and high loads are required.

Greases are sealingly applied to the actuators of the electric outside rear view mirrors mounted on various vehicles and the like to provide lubricity. Such greases are generally obtained by kneading a base oil and a thickener. At this time, synthetic lubricants such as mineral oil, ester oil, silicone oil and ether oil are used, and metal soap such as lithium soap or urea compound is used as a thickener. If necessary, various additives such as antioxidants, rust inhibitors, metal deactivators, viscosity index improvers, etc. may be used in the grease.

The life of the grease sealed to the actuator normally applied to the outside rear view mirror is shorter than the service life due to the fatigue of the actuator itself. As a result, the life of the outside rear view mirror actuator depends on the grease life, and there is an urgent need for grease with excellent durability.

Outside rear view mirrors are a key component of safety to ensure the driver's rear view and must operate smoothly in a variety of harsh environments. Therefore, the service life should be long, but it must be excellent in low temperature maneuverability, which can be started at low power under extremely low temperature conditions. However, when low viscosity base oil is used to maintain low temperature mobility, a thin oil film is formed at a high temperature, and thus oiliness becomes bad, causing noise. When using a high viscosity base oil to improve this, low temperature mobility becomes worse.

In addition, Korean Patent Registration No. 135414 discloses a synthetic base oil mixed with a poly-α-olefin having a high viscosity index and a poly-α-olefin having a low viscosity index, a thickener made of lithium composite soap, a PMA copolymer and additional additives. Although mixed grease compositions for ball joints have been disclosed, high temperature endurance life is not sufficient, despite the relatively high weight (25-50%) of PMA-based copolymers, and problems have arisen in silent operation. In order to improve the high temperature durability life, antioxidants, extreme pressure agents and the like have been conventionally added to grease, but sufficient effects are not obtained.

Accordingly, the present invention, in order to solve the above problems, by using a lithium-based core agent as a thickener while using synthetic hydrocarbon oil without using ester oil as base oil, to prevent degradation at high temperatures and to improve the high temperature life of grease In particular, when the PMA copolymer is used, the present invention has been found to be able to significantly improve low temperature maneuverability and high temperature durability as compared to conventional grease, and to improve viscosity index and adhesive performance.

Accordingly, an object of the present invention is to provide a grease composition for an actuator which uses synthetic hydrocarbon oil as a base oil and contains a lithium thickener and a PMA copolymer. In addition, an object of the present invention is to provide a grease composition having greatly improved low temperature maneuverability and high temperature durability.

The present invention provides a grease composition containing a base oil, a thickener and a copolymer, comprising: 75.0 to 85.0 wt% of base oil composed of synthetic hydrocarbon oil; Lithium thickener 5.0-17.0 wt%; And 0.5 to 10.0% by weight of PMA-based copolymer.

The present invention will be described in more detail as follows.

The present invention does not use ester oil as base oil, but instead uses synthetic hydrocarbon oil, and adds a lithium thickener and a PMA copolymer to improve compatibility with various materials including plastics, and has adhesiveness. In addition to the effects, the present invention relates to a grease composition which can improve the lubrication life of the application part in use at high and low temperatures and ensures noiseless operation and improved durability.

Although the base oil which can be used for this invention can be used if it is a base oil which can be normally used for grease, what does not affect plastics and rubber | gum is used. For example, synthetic hydrocarbon oils, mineral oils, or mixed oils thereof are preferable, but base oils based on synthetic hydrocarbons as a main component are more preferable. Examples of synthetic hydrocarbon oils include poly-α-olefin oils, copolymers of α-olefins and olefins, aliphatic hydrocarbon oils such as polybutene, aromatic hydrocarbon oils such as alkylbenzenes, alkyl naphthalenes, polyphenyls, synthetic naphthenes, and the like. can do.

The base oil containing the preferred synthetic oil as the main component of the present invention should have a kinematic viscosity of 30 to 100 cSt at 40 ° C and a pour point of 30 ° C or lower at low temperature. At this time, if the kinematic viscosity is less than 30 cSt, it is easy to evaporate, and heat resistance is insufficient. If the kinematic viscosity exceeds 100 cSt, the torque is large and the amount of heat is increased.

The preferred content of the base oil used in the present invention is 75 to 85% by weight, and if the base oil content is less than 75% by weight, it is too hard to be practically applied to grease. It is not preferable because there is a problem of liquefaction at high temperature.

In the present invention, a lithium thickener is used as the grease thickener, and a blending amount of 5.0 to 17.0 wt% is preferable based on the whole grease composition. At this time, when the content is less than 5.0% by weight, the liquid becomes low in viscosity and easily leaks, which makes it difficult to mount the actuator. Moreover, when it exceeds 17.0 weight%, it will harden | cure and it will become 200 or less, and it will lose practicality as grease.

Preferred lithium-based thickeners in the present invention can be represented by the following formula (1) and (2).

(R ₁ -COOLi) n

(R ₂ -COOLi) n

In Chemical Formulas 1 and 2, R ₁ and R ₂ represent an aliphatic hydrocarbon group having 6 to 20 carbon atoms, and n represents an integer of fatty acid lithium soap. At this time, if the carbon number is less than 6, the grease thickening property is inferior, and if the carbon number is more than 20, there is a problem that the heat resistance is worse.

The lithium thickener is obtained by reacting a lithium hydroxide compound with a fatty acid compound. In this case, in order not to leave a reactive fatty acid group, the fatty acid group of the lithium hydroxide and the fatty acid compound is preferably blended so as to be approximately equivalent. In addition, a lithium hydroxide compound and a fatty acid compound may be made to react in base oil, or the fatty acid lithium soap machine thickener previously synthesized may be mixed with base oil. However, the preferable manufacturing method is the former method which is easy to maintain the stability of grease.

On the other hand, the PMA copolymer used in the present invention is used for improving the viscosity index and adhesion properties to the base oil as 0.5 to 10.0% by weight relative to the entire grease composition, preferably less than 0.5% by weight PMA The viscosity index obtained by blending the system copolymer and the effect of improving the adhesion are insufficient, and when it exceeds 10.0% by weight, the base oil component which contributes to the lubricity is relatively small, which is not preferable. In the present invention, the viscosity of the base oil component can be improved by the action of the PMA-based copolymer during high-speed operation, and it is possible to significantly prevent the deterioration at high temperatures and to greatly improve the high temperature life of the grease.

PMA-based copolymers having improved adhesion to the base oil and viscosity index have a boiling point of 270 ° C. or higher, a pour point of 5 ° C. or lower, and a vinyl group (—C═C—) or a carbonyl group represented by the following Chemical Formulas 3 to 6 in the molecule: Copolymers having -COO-) are preferred. At this time, when boiling point is less than 270 degreeC, heat resistance will run short, and base oil will flow easily in high temperature, when a pour point is higher than 5 degreeC, cold resistance will run short and fluidity of base oil will fall in low temperature.

R ₃ COOR ₄

R ₅ COOR ₆ COOR ₇

R ₈ CH = CHR ₉

R ₁₀ CH = CHR ₁₁ COOR ₁₂

In the formulas (3) to (6), R ₃ to R ₁₂ represent a hydrocarbon number, and specifically, an aliphatic group, an aromatic group, or an alicyclic group of a saturated aliphatic group or an unsaturated aliphatic group. As a preferable PMA type copolymer, acrylate compounds, such as a styrene alkyl methacrylate type copolymer and a methyl methacrylate type copolymer, can be used.

On the other hand, the PMA copolymer has a viscosity index and improved adhesion performance to the base oil is, after filling a suitable amount viscometer with a base oil blended with a 7% weight PMA copolymer in a suitable amount viscometer and measured the viscosity of 40 ℃ and 100 ℃ It is said that it has the ability to improve the viscosity index that can maintain the value calculated above 200. In addition, a kinematic viscosity measurement is performed based on KS M2014.

The grease according to the present invention contains the base oil, the thickener and the PMA-based copolymer as essential components, but additives such as the extreme pressure additive, the antioxidant, and the corrosion inhibitor, which are conventionally added to the grease, can be blended.

By using a well-known extreme pressure agent together as an extreme pressure additive, load resistance and extreme pressure resistance can be improved. For example, the following compounds can be used. Examples of the organometallic compound include organic molybdenum compounds such as molybdenum dithiocarbamate and molybdenum dithiophosphate, organic zinc compounds such as zinc dithiocarbamate, zinc dithiophosphate and zinc phenate, antimony dithiocarbamate and dithi Organic antimony compounds such as antimony pentaphosphate, organic selenium compounds such as sethio dithiocarbamate, organic bismuth compounds such as bismuth naphthenate and bismuth dithiocarbamate, and organic iron compounds such as iron dithiocarbamate and iron octylate , Organic copper compounds such as copper dithiocarbamate and copper naphthenate, organic tin compounds such as tin maleate and dibutyl tin sulfide, or eutectic phosphates of alkali metals or alkaline earth metals, phenates, phosphenates, gold Organometallic compounds such as silver, titanium, cadmium and the like can also be used if necessary. As the sulfur compound, sulfides or polysulfide compounds such as dibenzyl disulfide, sulfurized fats and oils, ashless carbamic acid compounds, thiourea compounds, or thiocarbonates can be used. As a phosphate extreme pressure agent, phosphate ester compounds, such as a phosphate ester, such as toric octyl phosphate and a tricredil phosphate, an acidic phosphate ester, a phosphite ester, and an acid phosphite ester, can be used. In addition, other halogen-based extreme pressure agents such as chlorinated paraffin or solid lubricants such as boron compounds such as molybdenum disulfide, tungsten disulfide, graphite, PTFE, antimony sulfide and boron nitride can be used. Among these extreme pressure agents, a dithiocarbamic acid compound or a dithiophosphoric acid compound can be preferably used.

As antioxidant, it can select suitably from antioxidant, ozone deterioration agent, and antioxidant which are added to rubber | gum, plastic, lubricating oil, etc., and can be used. For example, the following compounds can be used. That is, phenyl-1-naphthylamine, phenyl-2-naphthylamine, diphenyl-p-phenylenediamine, dipyridylamine, phenothiazine, N-methylphenothiazine, N-ethylphenothiazine, 3,7-dioctylphenothiazine, p, p'-dioctyldiphenylamine, N, N'-diisopropyl-p-phenylenediamine, N, N'-di-sec-butyl-p-phenylenediamine Amine compounds, such as these, and phenolic compounds, such as 2, 6- di-tert- dibutyl phenol, etc. can be used.

As a corrosion inhibitor, the following compounds can be used, for example. That is, alkyl, such as ammonium salt of eutectic acid, alkali metals, such as barium, zinc, calcium, magnesium, the organic-technical acid salt of alkaline-earth metal, organic carbonate, phenate, phosphonate alkyl, or alkenyl zucic acid ester, Derivatives partial esters of polyhydric alcohols such as sorbitan monooleate, hydroxy fatty acids such as oleoyl zalcosine, mercapto fatty acids such as 1-mercapto stearic acid, or higher fatty acids such as metal salt stearic acid, isostearyl alcohol, etc. Higher alcohols; esters of higher alcohols with higher fatty acids; thiazoles 2- (decyldithio) -benzoimime such as 2,5-dimercapto-1,3,4-thiadiazole and 2-mercaptothiadiazole. Imidazole compounds such as dazoazole and benzoimidazole, disulfide compounds such as 2,5-bis (dodecyldithio) benzoimidazole, or phosphate esters such as trisnonylphenylphosphite, dira Thiocarboxylic acid ester type compounds, such as a uryl thio propionate, etc. can be used. Moreover, nitrite etc. can also be used.

The grease according to the present invention has the effect of preventing brittleness (creating cracks) and extending durability without adversely affecting plastics and rubbers by using synthetic hydrocarbon oils without using ester oils as base oils. By increasing the mechanical stability and water resistance, the PMA-based copolymer with base oil viscosity index and adhesion improves significantly and prevents deterioration at high temperatures and improves the high temperature life of grease. It can extend the life. In addition, low noise, low vibration operation can be ensured at all temperature / humidity conditions to meet the recently emphasized performance.

Hereinafter, the present invention will be described in more detail based on the following examples, but the present invention is not limited thereto.

Examples 1-3 and Comparative Examples 1-4

The base oil and the lithium-based thickener were combined with the composition shown in Table 1 below to prepare an actuator grease. The base oil shown in Table 1 was a poly-α-olefin oil (ExxonMobil, kinematic viscosity: 50 cSt at 40 ℃) as synthetic hydrocarbon oil. In addition, a lithium thickener is obtained by reacting lithium hydroxide with a hard caster oil (Tallow) which is a fatty acid compound. As the PEA copolymer, a styrene alkyl methacrylate copolymer [ACLUBE 1410, SANYO CHEMICAL INDUSTRY, Japan] was used as the PMA copolymer having a boiling point of 270 ° C. or higher and a pour point of 5 ° C. or lower. PIB used PB-680 manufactured by Daelim Industrial in Korea.

The base oil, the lithium-based thickener and the PMA-based copolymer were added in a total amount of 100% by weight, and a total of 3 parts by weight of a water-resistant enhancer, an antioxidant, and an anticorrosive agent were added to 100 parts by weight of the total grease composition.

Test Example

The kinematic viscosity of the base oil was measured in accordance with KS M 2014.

The measurement of the miscibility of base oil was performed according to ASTM D217.

Low temperature torque test of base oil was carried out in accordance with ASTM D4693.

In the operation noise test of base oil, after 5 hours storage at 90 ℃, the OUTSIDE REAR VIEW MIRROR was operated in four directions, and five or more evaluators evaluated the noise by ear.

As shown in Table 2, Examples 1 to 3 showed good results in the low-temperature torque showing the operability at low temperature and the operation noise test showing the quiet operation performance at the high temperature.

On the other hand, Comparative Examples 1 and 2 significantly improved the viscosity index of the base oil, and excluded the PMA-based copolymer that forms a film having a suitable thickness at high temperature, and friction noise occurred at a temperature of 60 ° C or higher. This friction noise reflects the inadequate lubrication of the steel worm and the polyacetal worm wheel inside the actuator, which is a remarkable durability. Causes deterioration. In order to form an appropriate lubricating film at a high temperature, in the comparative example in which olefin synthetic hydrocarbon oil having a viscosity of about 2 times higher than the base oil used in the grease of the present invention was used as a base oil, abnormal noise was generated at a temperature of 70 ° C. or higher. Due to the pour point limit of the olefin synthetic hydrocarbon oil, the low temperature torque is greatly increased, so that the load on the small motor for operating the actuator is increased and the durability is significantly decreased.

By comparing with the viscosity index of the base oil which is not mix | blended with PMA type copolymer, it turns out that the viscosity index of the base oil which mix | blended PMA type copolymer improves and is excellent in heat resistance.

In Comparative Examples 3 to 4, PIB (Polyisobutene), which has been widely applied to conventional lubricants, was added in the same composition as PMA for the purpose of improving the viscosity index and the adhesiveness. As a result, when 7.2% was added, it showed the same performance as PMA in noise prevention, but the torque at low temperature was greatly increased, and the durability of the actuator operated by a small motor decreased significantly. When the% was added, the noise protection performance decreased.

As described above, the actuator grease composition according to the present invention improves the compatibility with various materials including plastics, improves the lubrication life of the application site even when used at high and low temperatures while exhibiting adhesiveness, and operates silently and It is effective to ensure improved durability.

Claims (7)

A grease composition containing a base oil, a thickener and a copolymer, comprising: 75.0 to 85.0 wt% of a base oil composed of synthetic hydrocarbon oil; Lithium thickener 5.0-17.0 wt%; And 0.5 to 10.0% by weight of PMA (Poly Metha-Acrylate) -based copolymer. The grease composition for an actuator according to claim 1, wherein the base oil is composed of an aliphatic hydrocarbon oil or an aromatic hydrocarbon oil, having a kinematic viscosity of 30 to 100 cSt at 40 ° C, and a pour point of -30 ° C or less at low temperature. 3. The grease composition for an actuator according to claim 2, wherein the aliphatic hydrocarbon oil is poly-?-Olefin oil, a copolymer of? -Olefin oil and olefin or polybutene. 3. The grease composition for an actuator according to claim 2, wherein the aromatic hydrocarbon oil is alkylbenzene, alkyl naphthalene, polyphenyl or synthetic naphthene. The grease composition for an actuator according to claim 1, wherein the PMA-based copolymer has a vinyl group and a carbonyl group in a molecule having a boiling point of 270 ° C or more and a pour point of 5 ° C or less. 6. The grease composition for an actuator according to claim 5, wherein the PMA copolymer is a styrene alkyl methacrylate copolymer or a methyl methacrylate copolymer. The grease composition for actuator according to claim 1, wherein the lithium thickener is obtained by reacting a lithium hydroxide compound with a fatty acid compound.